#### Centre of mass

In finite objects, the total external force equals the total mass times the acceleration of a point called the centre of mass.

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Uniform circular motion: angular displacement and velocity are introduced and centripetal acceleration is determined.

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The total work done on an object equals the increase in its kinetic energy. For conservative forces, we can define potential energy.

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On scales much bigger than the wavelength, rays explain the behaviour of interfaces, mirrors, lenses, optical instruments, including telescopes and microscopes.

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The inverse square law explains planetary motion - and apples falling. Newton's law, measuring G, calculating orbits.

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Sound is produced in the larynx; filtering it in the vocal tract produces formants and phonemes. The acoustics, mechanics and some neurobiology of hearing. Pitch perception.

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Superposing waves with different frequencies gives beats and Tartini tones. Removing beats gives consonance. Tuning consonances gives temperament.

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p=mv. If external forces are zero, momentum is conserved. In collisions, energy may be conserved (elastic) or not (inelastic).

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Kinematics quantifies motion without explaining the causes of it. Here we study accelerations that are zero, positive or negative.

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F=ma (laws 1&2). Forces come in pairs that add to zero (3). Newton's laws apply in inertial frames of reference. Some common approximations made in applying them.

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Inertia and restoring forces can, with low friction or damping, lead to oscillations and resonance. We analyse the mechanics of vibrations.

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Motion with uniform acceleration, such as in a uniform gravitational (or electric) field is projectile motion, analysed here with examples.

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